Chlorination



Nov. 10, 1931. E, E. AYRES, JR

CHLORINATION Filed Feb. 4, 1927 www Patented Nay. 1o, 193i lUNITEDsTVATasfPATENT OFFICE EUGENE E. AYBES, JB., OF SWARTHMOBE, PENNSYLVANIA,ASSIGNOR T THEB. A. S. COMPANY, OF PHILADELPHIA, PENNSYLVANIA, ACORPORATION OF DELAWARE CHLORINATION Application led February 4, 1927.-Serial No. 165,875.

My invention relates to chlorination wherein hydrogen chloride isproduced and to the recovery of hydrogen chloride from a' mlX- turetherewith of a substance capable of formin a film on water.'

n chlorination by substitution, the products passing from thechlorinating step 1nclude hydrogen chloride, the chlorinated substance,and substances that are passed again through the ch'lorinating step andwhich consist chiefly of that fraction of the original substance to bechlorinated which was not chlo-y rinated in its passage through thechlorinating step. If chlorinated substances are returned to thechlorinating step they are very likely to be chlorinated to anundesirably hlgh degree, anditis, therefore, desirable to removechlorinated substances from the products of chlorination at sometimebefore un-I chlorinated substances in those pfoducts are returned to thechlorination step. It is desirable to redistill the chlorinatedsubstance Withdrawn from the products of chlorination. For example,whe'n pentanes are chlorinated amyl chlorides withdrawn from theproducts of chlorination, even by rectification, contain pentanes andhigher boiling chlorides. But, the chlorinated substances shouldbe drywhen redistilled, to avoid formation of hy-` drochloric acid as avresult of the decomposition of chlorides incidental to theredistillation. It is desirable, therefore, to withdraw chlorinatedsubstances from the products of chlorination priorto removal of hydrogenchloride therefrom by water absorption with consequent moistening of allother substances present. Introduction of moisture into the chlorinationmust be avoided, and it is desirable, therefore, that substances thatare to be returned to the chlorinating step be withdrawn, so far aspracticably possible', from the products of chlorination prior towaterabsorption therefrom of hydrogen chloride, and preferably afterremoval of chlorinated products by rectification. l A furtherdevelopment of my invention resides in so preparing products ofchlorination for return to the chlorinating step,in

cluding the removal therefrom of hydrogen,

chloride, that the requirements set out are niet and the difficultiesavoided. I

If it is attempted 'to absorb hydrogen Achloride from a mixture of gasesand vapors that contains a substance immisciblewith water, s uch-immiscible substance, if it is in liquid form or condenses during theabsorption operation, will form a ilm over the water surface and preventabsorption of the hydrogen chloride.

I have discovered that hydrogen chloride may be elfectively absorbedfrom a. mixture of vgases containing a substance that will form such aiilm on the water, provided that the absorption is carried out undercondi-l tions that maintain such a vfilm-forming substance in vaporphase throughout the absorptioir operation.

In the absorption of hydrogen chloride by water from the products of achlorinatin reaction, the lower the temperature at whic lthe absorptionis carried out the more concentratedwillbetheresultilg aqueoushydrochloric acid, other conditions, including the amount of water usedand the degree to which hydrogen chloride is removed, being unchanged.And, in the commercial absorption -of hydrogen chloride fromsuchvproducts, it

is desirable to carry out the absorption under such conditions that theuse of an amount of water which will result in the production of 22'Baum acid or higher will effect substantizlly complete removal ofhydrogen chlor1 e. a

Accordingly, a feature of my invention consists of absorbing hydrogenchloride with water from a mixture containing a film-forming' substance,while maintaining the temperature at which absorption takes place,4 thefilm-forming wlthin a range in which substance is in vapor form andaqueous h drochloric acid of desired concentration will be produced. Onemethod of so regulating the ktemperature "at which absor tion takesplace consists in re lating the ow of'cool-v ingwater for the a sorbingapparatus.

some mixturescontaining hydroowever gen chloride, containy afilm-forming subA -f stance that can be kept in vapor form by merecontrol of temperature, only at temperatures so high that the use of aquantity of absorbing water that will produce hydrochloric acid ofdesired strength, will not suiciently remove hydrogen chloride from themixture, and the use of enough water at such temperatures, to suicientlyremove the hydrogen chloride will produce hydrochloric acid ofundesirable low concentration. It is a feature of my invention undersuch circumstances, to add to the mixture containing hydrogen chlorideand the hlm-forming substances a sufficient quantity of gas of highvapor pressure to make it possible to carry out the absorption ofhydrogen chloride at such temperatures that the hydrogen chloride willbe suliciently eliminated from the mixture when hydrochloric acid ofdesired strength is produced. By 'carrying out the absorption operationat or near the highest temperature at which hydrogen chlorideelimination and production of suitably concentrated hydrochloric acidmay be eli'ected, the quantity of additional gas of high vapor pressureis kept at a minimum.

On the other hand, when substances of high vapor pressure are so addedthe temperature at which absorption is carried out can be reduced topoints below th maximum temperature atwhich complete removal of hydrogenchloride and production of acid of desired` concentration will occur,provided the proportion of the added substances is increased beyond theminimum. In some cases both temperature regulation and addition of highvapor-pressure gas may be necessary to pre-v vent film formation, whilein other cases it may be more convenient to prevent-film formation byadding high vapor pressure substances than by regulating .temperature ofabsorption, an example of the latter operation being the case wherelarge quantities of low temperature cooling 'water are availableA andthe film forming substances are pentanes.

In thepractice of my invention the temperature at which absorption iscarried out can be regulated b controlling the temperature and rate ofow of cooling water that takes heat from the apparatus in whichabsorption is elected; and substances of high vapor pressure added toprevent lm formation4 can be separated from the vapors passing from theabsorption operation by condensing the substances in those vapors, as bycompression or cooling or both, without condensing the added substances.The

' uncondensed added substances maythen be passed to the vapors enteringthe absorption operation. The condensed substances may be returned tothe chlorinating reaction.

In the practice of my invention a1r or any fixed as'that is chemicallyinactive under the exlsting conditions or low boiling hydrocarbons maybe used as the added substance of high vapor pressure; and thesubstances chlorinated may be aliphatic hydrocarbons or other substancesthat can be chlorinated by substitution and which are insoluble inwater.

lVhen the lowest boiling substances in the chlorination products fromwhich chlorinated substances have been removed are pentanes, it ispossible to keep them in vapor form during absorption by carefulregulation of the absorption temperature and still produce aqueoushydrochloric acid of desired concentration while suiiciently freeing thepentanes of hydrogen chloride; and my process is entirely Asuccessful inconnection with the chlorinationof pentanes and has contributedextensively to my commercial pract1ce thereof. It hexane is present somehigher-vapor-pressure substance such as butane must be added in anamount that will maintain the hexane in vapor phase in the absorber atthe temperature adopted to ensure complete absorption and suicientlyconcentrated acid.

'Io assist in the understanding of my invention, I have showndiagrammatically in the single figure of the annexed drawing, ap-

paratus whereby my invention may be prac ticed in connection withproducts of a chlorin- .ation reaction, it being understood, however,that my invention is not limited to that application thereof, and thatvariations may i the rectifying column 19. Ghlorides produced and someunchlorinated hydrocarbons are withdrawn through pipe 20 from therectifying column. Vapors from the rectifying column pass through pipe20a to condenser 21 from which condensedunchlorinated hydrocarbons passout through pipe 22 and may be passed again to the chlorinating reactionand a part of the' condensed hydrocarbon may be used as a retluxingliquid in column 19. Hydrogen-chloride-containing vapors pass fromcooler 21 through pipe 23 to the lower part of the hydrochloric acidabsorbing device 2 4 which may, as indicated,

consist of asinuous passage constructed of acid resisting material suchas silica-ware. Water is introduced by pipe 24a into the upper part ofabsorption-device24'. Aqueous hydrochloric acid is withdrawn from thelower part through pipe 25 and the remaining vapors, containingunchlorinated hydrocarbons, pass from the upper part of absorptiondevice 24 through pipe 26. The temperature at which absorption takesplace may'be controlled by the use of cooling water, discharging overthe absorption device 24 from pipe 240. For the further protection ofthe chlorinating equipment the l vapors passing through pipe 26 may beneutralized as by being passed into the lower part of neutralizingchamber 27 into the top of which a causticsoda solution is introduced bypipe 27 b, residual v caustic soda solution being withdrawn by y pipe27c 'from neutralizer 27.

Neutralized vapor may be passed by pipe la to compressor 37 and then toa cooler` 29 from which they are led into separator 30. `From the bottomof separator 30 water is withdrawn by ipe 31 and from a point above thebottom o the separator a pipe. 1b, containing relief valve 32,l conductscondensed hydrocarbonsto' a pressure release chamber 33. From chamber 33hydrocarbons are conducted through pipe 1 andmay be returned to thechlorinating reaction, preferably after being dehydrated. When thevapors passing through pipe 23 to the absorption device contain afilm-forming substance that can not be maintained in vapor phase withinthe absorber at a temperature suiiicientlylow to ensure that the vaporsmay be sufficiently freed of hydrogen chloride in the absorber and toensure that hydrochloric acid of desired strength will be produced, agasof high vapor pressure may be led into pipe 23 by pipe 36. s Thecompressing and condensing operations are so conducted that such addedgas is not condensed and it is withdrawn from separator 30 by ipe 34which returns it to pipe 23. Ifany o the added g'as of high vaporpressure is released' when the hydrocarbons pass from separator 30 to.chamber 33, that gas is conducted from" the chamber 33 by pipe 35 andintroduced into be used for effectively removing such added gas from theacid-freed substance.

It is apparent from the foregoing that the apparatus diagrammaticallyshown has provision for controlling the temperature of the absorber andprovisionl for maintaining gas of'highvapor pressure inthe absorber andrecirculating it thereto.

While I have described my invention and apparatus foruse in the practicethereof, in great detail, 'my invention is not limited to such detailsbut includes such-variations and modifications as fall within thehereunto appended claims. In this connection it is pointed out that if.some o r all of the unchlorinated hydrocarbon, or some or all of d i'the chlorinated substance, or some or all of no both, is passed into theabsorber, the conditions therein may be so controlled'.l as byregulation of temperature or introduction of as of high vapor pressure,or in both ways, t at such hydrocarbon and chloride will remain in vaporphase during the absorption ofthe pipe 34. Any desired apparatus mayhydrogen chloride; and suitable pressure and temperature conditions maybe maintained by the use of heating and cooling devices Yand valves andpressure vequalizing devices at suitable points including the valve 28for reducing the pressure of vapors entering the absorber.

Still referring to the chlorination of pentanes as an exemplaryapplication of my invention, I have carried out the chlorinationthereofas follows:

Vapor of pentanes formed at 85 C. to

100.o C. and at about 75 pounds gauge pressure and chlorine vapor at 40C. to 60 C. and at a pressure above pounds, have been brought togetherin the proportion of 15 to 20 parts pentane to one part chlorine (byweight), at about 85 C. to 100 C. under a pressure ofv 35 to 50 poundsand caused to react by heating toa temperature between 8 275 C. and 325C. Then the 'products of chlorinationwere cooled. to about C. to C.under a pressure of 15 to 25 pounds and introduced into a rectier fromwhich a mixture of amyl chlorides and pentanes was withdrawn'pin liquidform while a refiux of pentanes at .atmospheric temperature wasmaintained; The vapors leaving the rectifier Were at the boiling pointof pentane at the pressure used and were condensed'under a 95 pressurethat vwould cause the pentanes to liquefy at thetemperature of coolinwater available, for example, 10 pounds. ydrogen chloridewas'ab'sorbedby water under substantially atmospheric pressure and at atemperature approximating 37 C. to 43 C., the absorption of hydrogenchloride being substantially complete under those conditions and theaqueous hydrochloric acid having a concentration of 22 densation anddehydration of acid-freed vapors of pentanes passing from the absorptionstep being conveniently carried out under about 10 pounds of pressure.

' What I claim and desire to secure byl Letno permit .effectiveabsorption of hydrogen chlo- 12 .y i)

2. In the absorption of hydrogen chloride with water from a mixturecontaining a substance that would otherwise forml a film on water and,which may be maintainedin va- .por -orm under conditions` permitting'ab- 130 B. or higher, convaporphase at the'existing l sorption ofhydrogen chloride by water, the process comprising contacting themixture with water while maintaining the temperature of contacting highenough to maintain the substance in vapor phase, and low enough' topermit' absorption of hydrogen chloride by water to a commercialconcentration.

3. A process for absorbing hydrogen chloride with water in the presenceof pentane which' comprises contacting the hydrogen temperature ofcontacting suiiciently low to produce hydrochloric acid of not less than22 Baum. 5. A process for absorbing hydrogen chloride with water in thepresence of pentane which comprises contacting the hydrogen y chloridewith water while maintaining the temperature above but not substantiallyhigher than the boiling point of pentane at the pressure at whichcontact is made.

G. In the absorption of hydrogen chloride with water from a mixturecontaining a substance that would otherwise form a ilm on water andwhich may be maintained in vapor form under conditions permittingabsorption of hydrogen chloride by water, the process comprisingcontacting themixture with water while maintaining the vapor pressure ofthe substance suiiciently high to maintain the substance in vapor phaseand maintaining temperature and pressure conditions suitable toeffective absorption of hydrogen chloride in water.

7. In the absorption of hydrogen chloride with water from a mixturecontaining a-substance that would otherwise form a ilm on water andwhich may be maintained in vapor form under conditions permittingabsorption of hydrogen chloride by Wateri the process :omprisingcontacting the mixture with Water at a temperature suitable to effectiveabsorption of hydrogen chloride in water while maintaining the vaporpressure of the substances )resent in addition to hydro'en Chloride suciently high to prevent condensation of such substances at thetemperature. at which contact is made. A

8. In the absorption of hydrogen chloride with waterdfrom a mixturecontaining a substance that would otherwise form a film on water andwhich may be maintained in vapor forni under conditions permittingabsorption of hydrogen chloride by water, the process comprising"contacting thev mixture with water while maintaining the vapor pressureof the substances present inaddition to hydrogen chloride suicientlyhigh to prevent condensation of such substances at the temperature atwhich contact is made while maintaining the temperature of contactingsuiiiciently low to permit absorption to a commercial concentration.

9. A method of absorbing hydrogen chloride in Water in the resence of asubstantially water immiscib e' substance which may be maintained invapor form under conditions permitting absorption of hydrogenv chlorideby water which comprises contacting Water with the hydrogen chloride inthe presence of a water-immiscible substance havingy a. lower boilingpoint than the first mentioned substance at a temperature that-maintains the` irst mentioned substance in vapor phase and is lowenough to permit effective removal of hydrogen chloride.

l0. A method of absorbing hydrogen chloride in water in the presence ofa substantially water immiscible substance which may be maintained invapor form under conditions permitting absorption of hydrogen chlorideby water which comprises addlng y to the mixture a secondwater-immiscible substance of higher vapor pressure than thesubstantially water immiscible, substance and then contacting themixture with water While the iirst mentioned water immiscible sub-vstance is in vapor phase under conditions that permit effective removalof hydrogen chloride.

11. In the chlorination of pentane the process for the removal ofhydrogen chloride from products of chlorination which comprisescontacting with water the products of chlorination at a temperature highenough to f maintain the pentane in vapor phase and low enough to permitabsorption by the water of hydrogen chloride to a commercialconcentration.

12. A process for the separation of substances one of which is solublein Water and one of `which issubstantially immiscible with A 13. In theabsorption of hydrogen chloride with water from a mixture containing asubstance that would otherwise form a film on water andwhich may bemaintained in vapor form under conditions permittmg absorption ofhydrogen chloride by water, the process comprising contacting lthemixture with water while 'maintaining such temperature and pressure atthe point of contactmgthat the substance will be in vapor phase andhydrogen chloride will be suiiiciently absorbed in the Water to produceaqueous hydrochloric acid of commercial strength.

111-. In the chlorination of hydrocarbons inimiscible with Water andwhich would otherwise be in liquid phase in the water-absorption ofhydrogen chloridev therefrom, the steps comprising removing chlorinatedsubstances by rectiiicatio'n from the products of chlorination,contacting remaining products with Water under conditions of temperatureand pressure and vapor tension of the substances present that maintainAthe hydrocarbon in vapor phase andl permit effective removal of .thehydrogen chloride, and passing the acid-freed hydrocarbon back to thechlorinating operation.

15. In the chlorination of pentanes, the steps comprising removingchlorinated pentanes by rectification from the products of chlorination,contacting remaining products including hydrogen chloride with WaterWhile maintaining the pentanes in vaporl form at a. ten'iperaturepermitting substantially complete removal of hydrogen chloride andproduction of aqueous hydrochloric acid of commercial strength, andreturning pentanes substantially freed of acid and of chlorides ofpentanes to the chlorinatin 16. In the absorption of hydrogen chlloridewith Water from a mixture containing a substance that would otherwiseform a Iilm on the Water and which may be maintained in vapor form underconditions permitting absorption of hydrogen chloride by water, theprocess comprising contacting the mixture with water While maintainingconditions of temperature and pressure and vapor tension of thesubstances present that preserve said film-forming substance in vaporphase and permit effective absorption of hydrogen chloride by water.

In testimony whereof, I have signed my name to this specification.

n EUGENE E. MREs-,JaI

